The field of the invention relates generally to fiber optic networks, and more specifically, to methods and systems for providing full avionics data services over a single fiber using two wavelengths. Full data services, at least it relates to an avionic computer, generally means transmission and/or reception of mission data (control and/or sensing), health maintenance status, and configuration data loading.
The electrical data links utilized in most aircraft incorporate a first twisted pair of conductors to transmit signals, and a second twisted pair of conductors to receive sensing and/or control data. In addition, interfaces for file transfer functions such as configuration data loading and health maintenance data are also required and utilized. While about 10% of aircraft data links are high speed backbones that often require full duplex operation such as a switched network, the other 90% are lower speed access networks that typically use half duplex operation on a multicast or bus network. Typically, aircraft sensing and/or control data is periodically transmitted (or received) and these messages are generally a fixed size. File transfer data messages are not periodic. Instead, file transfer data messages are transmitted on demand and are generally of irregular file size. Data loading messages are necessary to change the configuration of airborne computing equipment to adapt to different computing applications and flight missions.
Health maintenance messages are one type of file transfer data messages that are incorporated and utilized to report health status of aircraft equipment for fast maintenance action and avoidance of long turn around time at an airport. Due to increasing functionality and capability of avionic equipment, health maintenance and configuration data have increased exponentially for each new aircraft configuration. Navigation databases and intelligent engine messaging are relevant examples of applications with large amounts of configuration and health maintenance data.
Such data can take several hours to transfer, however, turn around times at airport terminals are generally limited to about fifteen minutes. It is relatively easy to contemplate that it is costly for an aircraft to be grounded for maintenance. Typically, health maintenance data is time shared with control data on the same data link. Therefore, bandwidth would be reduced and the latency and jitter of the critical control data would be increased to accommodate the additional health maintenance data traffic.
Ideally, multiple pairs of copper wiring are used to send and receive sensing data, control data, configuration data, and health maintenance data. In a typical scenario, a file to be transferred, such as a health maintenance data file, is disassembled into dozens or hundreds of smaller pieces, so the transmission of this data can be time multiplexed with control data in the same stream. These pieces must be reassembled into the health maintenance data file at the receiving end. When time multiplexed, configuration and health maintenance data is time shared with control data on the same data link. Transmission of health maintenance data, for example, reduces the bandwidth available for the control data in order to accommodate additional health maintenance data traffic. One possible result is additional latency and jitter of the critical control data, since the computer has to perform tasks to separate the different data types and disassemble (or reassemble) data files as mentioned above.
File transfer data messages such as health maintenance messages must either be time shared with control data on a single data link or enabled utilizing a separate data link. Although the loading of new configuration data for an article of aircraft equipment can be delayed and performed at a convenient time, such as when the subject computer is not in mission operation mode, the health maintenance data needs to be transmitted concurrently to provide for the desired goal of fast maintenance actions. It is desirable to perform configuration data loading processes in real time, for example, to reconfigure one or more avionics computers “on the fly” to adapt to different phases of a single flight.
Entities involved with health maintenance data have been requesting dedicated health maintenance data links, utilizing separate wiring, for some time to help reduce airline operation cost. For this desired simultaneous and non interfering operation, additional electrical cabling and connectors must be added to each aircraft computer (which are sometimes referred to as line replaceable units (LRUs)). Unfortunately, such a solution increases LRU and aircraft costs, increases aircraft weight, and affects volume, installation and maintenance considerations.